Surrogate reactions are a powerful tool to access neutron-induced reaction cross sections of short-lived nuclei. However, to infer neutron-induced reaction cross sections from measured deexcitation probabilities requires a consistent and rigorous theoretical framework describing both charged-particle and neutron-induced reactions. This work presents the first practical application of the new approach developed in O. Bouland, Phys. Rev. C 100, 064611 (2019) to Pu fissile isotopes, 237,238,240,242,244Pu*. Average neutron-induced reaction cross sections and deexcitation probabilities measured in surrogate reactions are simultaneously analyzed with an efficient Monte Carlo R-matrix-extended theory algorithm using a unique set of nuclear-structure parameters to describe both observables. Fission probabilities allow one to estimate fission-barrier heights, not otherwise accessible in fissile isotopes. The theoretical framework is here extended to model 'giant' resonance structures observed in the fission probabilities of some nuclides. A careful study of the impact of the uncertainties on nuclear parameters and on the populated compound system angular distribution has been carried out. This study raises questions on the normalization of some fission probabilities measured in the 70's in (t,p) reactions, that could not have been pointed out without the use of the here-presented complex technique. This finding is especially important for the peculiar 240Pu* system. In addition, our study reveals for the 237Pu* compound system a 10 to 30% too high value of the only-performed low-energy neutron-induced fission cross section measurement (Gerasimov et al., JINR-E–3-97-213 (1997)) and, subsequently of the evaluated fission cross section below 50 keV for the 236Pu.

中文翻译：

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首次同时评估 Pu 裂变同位素的裂变概率和中子诱导截面


替代反应是获得短寿命原子核的中子诱导反应截面的强大工具。然而，要从测得的去激发概率推断中子诱导的反应截面，需要一个一致且严格的理论框架来描述带电粒子和中子诱导的反应。这项工作首次将 O. Bouland， Phys. Rev. C 100， 064611 （2019） 中开发的新方法应用于 Pu 裂变同位素 237,238,240,242,244Pu*。在替代反应中测量的平均中子诱导反应截面和去激发概率与高效的蒙特卡洛 R 矩阵扩展理论算法同时使用一组独特的核结构参数来描述这两种可观察对象。裂变概率允许人们估计裂变势垒高度，这在裂变同位素中是无法获得的。理论框架在这里扩展到模拟在一些核素的裂变概率中观察到的“巨型”共振结构。已经对不确定性对核参数和填充复合系统角度分布的影响进行了仔细研究。这项研究提出了关于 70 年代在 （t，p） 反应中测量的一些裂变概率归一化的问题，如果不使用这里提出的复数技术，就无法指出这些问题。这一发现对于奇特的 240Pu* 系统尤为重要。此外，我们的研究表明，对于 237Pu* 化合物系统，仅执行的低能中子诱导裂变截面测量（Gerasimov 等人，JINR-E-3-97-213 （1997））以及随后评估的 236Pu 裂变截面低于 50 keV 的值高了 10% 到 30%。